1. Field of the Invention
The invention relates to a drive means for a motor vehicle door lock or the like, but also to a motor vehicle rear hatch lock or rear door lock or tailgate lock, with an electric motor drive, a gearing having a drive side and a driven side, an actuating lever of a lock mechanism in driven connection with the gearing.
2. Description of Related Art
The known drive means for a motor vehicle door lock or the like has a simple structure and allows simple auxiliary actuation by hand when the electric motor drive fails U.S. Pat. No. 5,240,296). In this drive means the gearing is made as a worm gear pair with a worm and worm gear, projecting eccentrically from the worm gear in the axial direction a driving lug which fits into a fork-shaped receiver of an actuating lever and overthrows it into a safety or safety-released position. The driving lug is at rest outside the fork-shaped receiver so that then the actuating lever can be moved back and forth by hand between the safety and safety-released position. When the electric motor drive fails, therefore the lock can also be moved by hand into this rest position, i.e. for example, the safety can be engaged or released proceeding from a locking cylinder.
In this prior art stops for the safety position and the safety-released position are assigned to the actuating lever. Actual activation ofthe electric motor drive takes place by microswitches, not by striking these stops.
One problem in this drive means is the failure of electricity while the electric motor drive is running. Then it can happen that the driving lug on the worm gear remains within the fork-shaped receiver, is blocked there, and thus locks the entire door lock. Usually it is not possible to build the electric motor drive such that it does not self-lock in this situation, therefore can be reset by hand when the corresponding force is applied.
If the intention is to control the electric motor drive by so-called "block operation", i.e. by fixing the power consumption when the driving lug strikes the stop surfaces laterally from the fork-shaped receiver published German Patent Application No. 44 39 479), it is admittedly advantageous in terms of motor and control engineering, but the aforementioned problem of drive failure during operation is thus not solved. In addition, the impact when the driving lug strikes the stop surface is hard; this can lead to considerable wear and premature failure of the drive means and briefly cause the current to rise very dramatically (6 to 8 A). Making the corresponding stops elastic does not always help the situation published European Patent Application No. (0 684 356).